If there is NO window, then yes you must install an exhaust fan. Theoretically, with no window, sewer gas "could" back up into the room and create a hazardous environment. Never mind most people would not open the window, especially in cold weather. But if it's there and the room is filled with noxious fumes, it can provide an outlet for release of noxious gases.

: : : My builder roughed in the plumbing, but I don't see any hardware for an exhaust fan. Since it sounds like most building codes require a fan in a bathroom, what do I do to vent the bathroom. This room will only have a toilet and sink, no shower.: : : Thanks.

: : Reply:: : As far as I know, a powder room, (w.c. & lav) is only required to have an exhaust fan if there isn't a window. Check your local code.: : e-plumber

: In my area we rough in the plumbing under slab but not the exhaust fan. It relates to a finishing expense that does not need to be included in the initial purchase of a house.: LonnythePlumber